Currently, mobile devices configured for the reception of digital television programmes are based on standard technologies such as OMA (Open Mobile Alliance), DVB-H (Digital Video Broadcast, Handheld), or DMB (Digital Multimedia Broadcasting) which is in a way a broadband extension of DAB (Digital Audio Broadcasting).
The OMA technology implements a single complete solution for a given market such as the portable phone market where all devices and content providers implement the OMA technology.
DVB technology has been designed to standardize digital television decoders (set-top boxes) in order to reduce their costs on a large scale. It standardizes the elements involved in the conditional access to content broadcast in MPEG-2 or MPEG-4 formats for mobile television on the Internet. These elements consist of the encryption algorithm of the broadcast content, the ECM control messages containing the decryption keys or control words, the EMM management messages containing user entitlements and the interface between the decoder and the security module managing the conditional access.
In the particular case of DVB-H mobile television, the protection of the content is developed by the DVB-CBMS group (Digital video Broadcasting—Convergence of Broadcast and Mobile Services).
The standardization does not encompass either the added value content of the ECM and EMM messages, or the method of protection of said messages. Each conditional access provider uses its own data structure and its own protection means for a particular broadcast content. DVB technology thus offers a number of possibilities for the development of content security.
It is well known for a broadcaster to be allowed to manage the reception of an event depending on geographical location. In fact, broadcasters will often try to preclude the access to content such as a sports broadcast in the area surrounding the site where this event takes place. Thus, by knowing the location of each receiver, a so-called <<blackout>> signal is sent to the receiver with for instance the postcode or postcodes of areas which are not allowed to receive live coverage of the event. The security module of the receiver that contains the location information (for example the subscriber postal code to the service or ZIP code), receiving this message, will thus apply a new rule during the entitlements verification and even if the receiver has entitlements for this event, the <<blackout>> message has priority to forbid the access to the event by not sending back the control words that are used to encrypt the event.
Nevertheless, in the mobile universe, this notion of “postal code” is no more valid and it is not possible to restrict a reception on such a portable device.